One known electric power converter is described in an “Electric power converter, and 2-power source system vehicle carrying same” in Japanese Kokai Patent Application No. 2006-25518. In this power converter, electric power is fed from plural power sources so as to drive a motor at high efficiency.
In the motor driving system described therein, plural power sources are connected in parallel to form a power source system. By feeding electric power to the motor from three or more potentials including a common potential, it is possible to drive the motor at any electric power allotment. In this way, it is possible to feed driving electric power to the motor from plural power sources simultaneously without having a DC-DC converter. As a result, it is possible to suppress loss and to realize high energy efficiency.